1. Field of the Disclosure
The present disclosure relates to a radio frequency (RF) power amplifier; in particular, to a RF power amplifier with temperature compensation.
2. Description of Related Art
In a wireless hand-held communication device, a main direct current (DC) power consumption comes from a RF power amplifier. Therefore, to keep a high linearity of the RF power amplifier without an amplified signal being distorted and to maintain a high efficiency to support a long time of communication has always been a focus in designing the RF power amplifier. In particular, there is an obvious characteristic of a time-dependent wave packet when a broadly used digital modulation technique of orthogonal frequency-division multiplexing (OFDM) is adopted in a wireless communication system, and a constant of peak to average power ratio (PAPR) of which is way higher than that of the current wireless communication system; in other words, the variation of the wave packet with time is more dramatic, and thus a demand of the linearity of the RF power amplifier is higher.
In the prior arts, a bandgap reference circuit used as a bias circuit in a power amplifier is able to provide a reference voltage with a close to zero temperature coefficient; however, as a transistor in the power amplifier is a bipolar junction transistor and which results in a characteristic of a negative temperature coefficient of a current gain, and the current gain (Beta) decreases with an increasing temperature, and further leads to a problem of reducing in output current and output power; therefore, there is a secret worry that a low linearity of power amplifier leads to the amplified signal being distorted.